ServiceNow instance URL (i.e. xyz.service-now.com) is not accessible from the MID server host even though the whitelisting of the specific instance IP is configured.
ServiceNow Instance with any version.
- Specific instance IP which is whitelisted is mapped to another instance as well due to which instance URL couldn't be accessed from the MID server hosts.
i.e. xyz.service-now.com and abc.service-now.com instances are mapped to same IP 127.0.0.1 (this is just an example)
- This can be tested by using ping <instance_name.service-now.com> (or) nslookup <instance_name.service-now.com> command from the MID hosts.
- Generally, when whitelisting/blacklisting the DNS name should be taken into consideration rather than the IP address.
- Because when a specific node gets reassigned to a new node for an instance the IP address will get changed eventually, but not the DNS name which will be unique (unless and until if there has change proposed to reconfigure the DNS name)
- At this stage when the new node gets assigned to the specific instance the IP address will get reassigned in turn, which will cause access related issues.
- So whitelisting has to be configured against the DNS name along with the port 443 and not against the IP address.